The Binding of Selected Therapeutic Drugs to Human Serum α-1 Acid Glycoprotein and to Human Serum Albumin In Vitro

The binding of acetaminophen, lidocaine, phenobarbital, phenytoin, theophylline, and valproic acid to human serum alpha-1 acid glycoprotein (orosomucoid) and to human serum albumin separately in vitro was investigated using equilibrium dialysis of the unlabeled drugs. Each drug was studied at a therapeutic concentration. Alpha-1 acid glycoprotein was studied at one elevated and two physiological concentrations, whereas albumin was studied at one physiological and two low concentrations. The nonphysiological concentrations were consistent with those that might be seen in a variety of clinical conditions. Acetaminophen, phenobarbital, theophylline, and valproic acid showed negligible binding to alpha-1 acid glycoprotein. However, lidocaine and phenytoin demonstrated binding to this protein, and increases in the alpha-1 acid glycoprotein concentration produced decreases in the unbound (free) or "active" concentration of these two drugs. All drugs but acetaminophen bound to albumin, and decreases in the albumin concentration yielded increases in the unbound (free) or "active" concentration of the remaining 5 drugs. These findings are significant when lidocaine, phenytoin, phenobarbital, theophylline, or valproic acid are used in patients with clinical conditions that may affect the concentration of these two binding proteins.

Immunological similarity of CEA with alpha 1-acid glycoprotein (orosomucoid)

We have demonstrated that 125 I-CEA (carcinoembryonic antigen) from two commercial sources (Roche and CIS RIA kit) can be precipitated by antibody to alpha 1-acid glycoprotein (AG) dose-dependently. The binding of 125 I-CEA to anti-AG can be displaced by unlabelled AG, though, there was no cross-reaction between AG and anti-CEA. The data strongly suggest that CEA has an immunological similarity to AG. The perchloric acid extract from cancerous tissue was fractionated on a Sephadex G-200 column, and the first eluted fraction (containing large amounts of CEA) was subjected to affinity chromatography using anti-AG bound to Sepharose. The bound fraction was eluted, labelled with 125 I, and then applied to a Sephadex G-200 column with carrier protein. The radioactivity was found mainly in the large molecular size eluted fraction (Fr 1). Almost all radioactivity of Fr 1 was precipitated by anti-AG and anti-CEA. This experiment also demonstrated that a large molecular weight component (Mr: 180 000) obtained from tumor was immunologically related to both CEA and AG. Based on differences in binding affinities between CEA with anti-CEA and with anti-AG we postulate that CEA may be a large molecular precursor of AG (big form of AG).

Enzymes as versatile labels and signal amplifiers for monitoring immunochemical reactions

Enzymes have proven to be sensitive and versatile labels for immunochemical assays. The sensitivity of an enzyme label stems from its extraordinary catalytic power which in turn provides a great amplification of signals. Its versatility, however, stems from the fact that enzyme activity can be modulated by a number of substances. Enzyme labeled immunoassays can be divided into two categories: (a) heterogeneous and (b) homogeneous (non-separation). In the heterogeneous systems, the quantitation of the antibody bound and unbound fractions requires a physical separation of these two fractions, whereas the homogeneous or non-separation systems do not require such a separation. In the homogeneous systems, the unbound and antibody bound fractions can be distinguished functionally. A total of 11 unique principles used in the development of enzyme labeled immunoassays are described. The advantages, disadvantages and limitations of them are considered, as well as the future paths for research and developments.

Plasma alpha 1-acid glycoprotein levels in pregnancy

One hundred and five determinations of plasma alpha 1-acid glycoprotein (alpha 1AG) levels in 96 women with normal pregnancies were done by an enzyme-linked immunosorbent assay developed in this laboratory. Plasma alpha 1AG levels in pregnant women of all trimesters and 4-10 weeks post-partum period do not differ significantly from those obtained from healthy women of child bearing age. In nine women whose pregnancies were complicated by acute inflammation, plasma levels of alpha 1AG were significantly higher. These findings suggest that in normal pregnancy, alpha 1 AG levels in the plasma remain unchanged. But, pregnancy does not obscure alpha 1 AG response to acute inflammation.